It's not just Google. Whilst I don't disagree with Zarko, I would like to impress that if a hub is only of interest to Google and no-one likes it enough to read it, then it's likely that the adverts won't get clicked as much as they would if readers did. I may be wrong here, but if you can't get the reader's interest, why would they click on the adverts?
Plain text hubs tend, in my opinion, to be less interesting to readers than those with some form of illustrative content to augment the text.
As Zarko said, adding a topical caption - which may also include keywords - to each of the pictures you add to the hub, will only help as far as Google is concerned.